Same, row DD, seat 11. The final soundlevel is almost the same, but in this seat itis mostly reflections. LOC =-1.1dB

Note the window defined by the black box. We propose that if the areaunder the direct sound is greater than the area under the red line, thesound will be CLEAR. The ratio of these areas is LOC (in dB).

And the following equations:

•We can use this simple model to derive an equation that gives us a decibel valuefor the ease of perceiving the direction of direct sound. The inputp(t)

is the soundpressure of the source-side channel of a binaural impulse response. (700-4000Hz)

–We propose the threshold for localization is 0dB, and clear localization and engagement occur at alocalizability value of +3dB.

•WhereD

is the window width (~ 0.1s), andS

is a scale factor:

•Localizability (LOC) in dB =

•The scale factorS

and the window widthD

interact to set the slope of thethreshold as a function of added time delay. The values I have chosen (100ms and-20dB) fit my personal data. The extra factor of +1.5dB is added to match mypersonal thresholds.

•Further description of this equation is beyond the scope of this talk. Anexplanation and Matlab code are on the author’s web-page..

•Reverberation and reflections without precise localization of sources isperceived as in front of a listener.

–In nearly all halls

itis

in front.

•When direct sound is added just above the threshold of audibilityreverberation is perceived as louder and all around the listener.

•The effect is perceived at all frequencies, even if the direct sound is band-limited to the 1kHz or 2kHz octave bands.

•When the pitch, timbre, location, and distance of a source can be perceived atthe onset of a sound we perceive these properties as extending through thesound, even if later reverberation overwhelms the data in the direct sound.

•When–

as in a recording–

the reverberant level is low, we perceive thereverberation as continuous, even if the direct sound overwhelms it.

Conclusions

•We have proposed that amplitude modulations of the basilar membrane at vocal formantfrequencies is responsible for

–Making speech easily heard and remembered,

–Making it possible to attend to several conversations at the same time,

–And making it possible to hear the individual voices in a music performance.

–A model based on these modulations predicts a great many of the seemingly magical properties of humanhearing.

•Although some of the consequences of this research for hall, stage, and classroom design mightseem controversial or disturbing, they can be and have been demonstrated in real rooms.

•The power of this proposal lies in the simple physics behind these hearing mechanisms. Therelationships between acoustics and the perception of timbre, direction and distance of multiplesound sources becomes a physics problem .

–How much do reflections and reverberation randomize the phase relationships and thus the informationcarried by upper harmonics.

•A measure,LOC,

is proposed that is based on known properties of speech and music.

–In our limited experience LOC predicts–

and does not just correlate with–

the ability to localize soundsources simultaneously in a reverberant field. It may be found to predict the ease of understanding andremembering speech in classrooms, the ease with which we can hear other instruments on stages, and thedegree of envelopment we hear in the best concert halls.

•A computer model exists of the hearing apparatus shown in the model slide.

–The amount of computation involved is something millions of neurons can accomplish in a fraction of asecond. The typical laptop finds it challenging.

–Preliminary results indicate that a measure such as LOC can be derived from live binaural recording of musicperformances.